HD 42818
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Camelopardalis |
| Right ascension | 06h 18m 50.7809s |
| Declination | +69° 19′ 11.176″ |
| Apparent magnitude (V) | +4.76 |
| Characteristics | |
| Spectral type | A0 Vn |
| B−V color index | 0.025±0.003 |
| Astrometry | |
| Radial velocity (Rv) | −7.0±7.4 km/s |
| Proper motion (μ) | RA: +0.686 mas/yr Dec.: −108.270 mas/yr |
| Parallax (π) | 18.64±0.23 mas |
| Distance | 175 ± 2 ly (53.6 ± 0.7 pc) |
| Absolute magnitude (MV) | +1.11 |
| Details | |
| HD 42818 A | |
| Mass | 2.49 M☉ |
| Radius | 2.7 R☉ |
| Luminosity | 33.83 L☉ |
| Surface gravity (log g) | 4.18±0.14 cgs |
| Temperature | 10,834±368 K |
| Metallicity [Fe/H] | 0.3 dex |
| Rotational velocity (v sin i) | 255 km/s |
| Age | 99 Myr |
| Other designations | |
| BD+62°628, FK5 234, HD 42818, HIP 29997, HR 2209, SAO 13788 | |
| Database references | |
| SIMBAD | data |
HD 42818 is a suspected astrometric binary star system in the northern circumpolar constellation of Camelopardalis. It is visible to the naked eye with an apparent visual magnitude of +4.76. Based upon an annual parallax shift of 18.64±0.23 mas as seen from Earth's orbit, it is located some 175 light years away. The system appears to be moving closer with a heliocentric radial velocity of −7 km/s. As of 2012, it is estimated that the system will make its closest approach to the Sun in 485,000 years at a distance of around 169.2 ly (51.87 pc).
The visible member, designated component A, is an A-type main-sequence star with a stellar classification of A0 Vn, where the 'n' indicates "nebulous" absorption lines due to rotation. It is spinning rapidly with a projected rotational velocity of 255 km/s (van Belle (2012) lists 325 km/s), giving the star a pronounced equatorial bulge. Although spectral type A stars are not expected to emit X-rays, the coordinates of this star is a source of X-ray emission with a luminosity of 120.4×1020 W. This may be coming from a cooler, unseen companion.
The primary has an estimated 2.49 times the mass of the Sun and about 2.7 times the Sun's radius. It is a relatively young star, about 99 million years old. The star is radiating 34 times the Sun's luminosity from its photosphere at an effective temperature of 10,834 K.